To make the fudge sauce, combine the ingredients in a small saucepan. Stir with a metal spoon over a medium heat until the chocolate has melted and the sauce is smooth. Remove from the heat and transfer to a bowl.
Place icing sugar into a sieve. Brush one side of a tortilla with melted butter and sprinkle with 1 teaspoon of icing sugar. Turn and repeat on the other side. Heat a medium sized frying pan over a medium heat. Place tortilla in the hot pan and cook for 2 minutes until golden and caramelized, turn and cook for a further 1-2 minutes.
Place a sheet of baking paper over a rolling pin, while tortilla is hot, quickly hang over the rolling pin and allow to set. Repeat with remaining butter, sugar and tortillas.
Cut, peel and chop the mango and place into a bowl. Add the blueberries, raspberries and grapes.
Spoon the cream, yoghurt or softened ice cream into the base of each taco. Top with fruit salad then drizzle with fudge sauce. Serve.